The electrical system of a motor vehicle may be powered using a generator.
Moreover, the electrical system of certain vehicles, e.g., safety vehicles, ambulances and commercial vehicles, may be supplied with energy using at least two generators, in order to be able to ensure the required power demand and/or the required reliability of the electrical supply.
The wear, and therefore also the service life of a generator depends on several factors. One of these factors is its electrical capacity utilization. The greater the electrical capacity utilization of a generator, the greater its wear and the lower its remaining service life. Therefore, it is desirable to be able to control the capacity utilization of the generators used according to strategies specific to the application. For example, application-specific strategies are a uniform capacity utilization or a very one-sided distribution of the capacity utilization.
German Patent document DE 10 2005 12 270.1 discusses a method and a device for providing the supply voltage for the loads of a vehicle electrical system, using several generators. A regulating unit having at least one power transistor is assigned to each of the generators. In order to bring the degree of capacity utilization of the generators into agreement, in one of the regulating units, a pulse-width-modulated control signal or a control signal derived from it and describing the pulse duty factor of the pulse-width-modulated signal is formed and supplied to the power transistors of all regulating units.
Moreover, a device having generators connected in parallel is discussed in German Patent document DE 41 08 861 A1. In this device, a voltage regulator is assigned to each of the generators. The device also has at least one battery whose one terminal is connectable to the voltage regulator via an ignition switch. Furthermore, a charge-indicator device is provided which is connected to the ignition switch and the voltage regulators, and is connectable via a circuit element to the negative terminal of the battery which may be connected to ground. Between the charge-indicator device, the voltage regulators and the indicated circuit element is a circuit configuration having a plurality of components conductive in one direction and blocking in one direction. To be achieved by this device is that a high electrical power can be produced by the use of two generators, and that faults occurring in one of the two generator/voltage-regulator systems can be indicated by a single indicator, e.g., a charge-indicator lamp, while the other generator/voltage-regulator system can continue working without problem.